The invention relates to a motor-vehicle door latch having
a pivotal latch member and pawl, and
a lever actuating system and a latching-lever system, and
a central-locking drive for a central-locking element, the central-locking drive has at least one eccentric control pin which moves along an arcuate path and that can engage in a first fork seat of the central-locking element to establish xe2x80x9cunlockedxe2x80x9d and xe2x80x9clockedxe2x80x9d positions and where the control pin is also movable into an xe2x80x9cantitheftxe2x80x9d position. The lever locking system normally comprises an outside latching mechanism and an inside latching mechanism. The outside latching mechanism is typically provided with a locking cylinder and locking nut. The inside latching mechanism has at least an inside latching lever. The actuating lever system comprises in general an outside door handle and an inside door handle.
With a motor-vehicle door latch of the above-described type an additional coupling lever is provided which connects a latching lever with the actuating lever system. In the xe2x80x9cantitheftxe2x80x9d position the control pin blocks the coupling lever via an additional antitheft element on the coupling lever. Such a system is fairly effective, but is somewhat expensive to manufacture due to the described separate antitheft element (see DE 195 33 199).
In a similar system a Y-shaped cutout is provided in the central-locking element. Inside this cutout are control surfaces against which engages a control pin so as to in this manner pivot the central-locking element. In the antitheft position, as shown there in FIG. 1, the central-locking element is also arrested by means of the known central-locking drive. Thereafter a mechanical unlocking is not actually possible (see U.S. Pat. No. 5,240,296).
The invention is aimed at the technical problem of so improving a motor-vehicle door latch of the above-described construction that flawless operation is obtained with the fewest possible parts.
This object is achieved according to the invention in that, starting from a motor-vehicle door latch of the above-described type, the central-locking element also has in addition to the first fork seat a second fork seat, these two fork seats extending partially into the arcuate path of the control pin. According to a preferred embodiment, the two fork seats are formed on a common arc of an arcuate segment of the central-locking element. Overall, the two fork seats form four control surfaces in order to be able to follow the following commands:
a) lock;
b) unlock (from the xe2x80x9clockedxe2x80x9d position);
c) antitheft; and
d) unlock (from the xe2x80x9cantitheftxe2x80x9d position).
Of course there can be more than four control surfaces when there is a third fork seat.
The central-locking element can have a central-locking pin that assumes together with the central-locking element the xe2x80x9cunlocked,xe2x80x9d xe2x80x9clocked,xe2x80x9d and xe2x80x9cantitheftxe2x80x9d positions. Finally the central-locking element is pivoted by the central-locking drive into the three identified positions. At the same time these positions are retained in that the central-locking element in the xe2x80x9cunlocked,xe2x80x9d xe2x80x9clocked,xe2x80x9d and xe2x80x9cantitheftxe2x80x9d positions is arrested by end abutments in the housing and/or by catches.
Preferably the latching-lever system has the above-mentioned inside latching lever cooperating with the central-locking element in the xe2x80x9cunlockedxe2x80x9d and xe2x80x9clockedxe2x80x9d positions. In other words, the xe2x80x9cantitheftxe2x80x9d position is when the inside latching lever and the central-locking element, as is usual, are not connected with each other, some coupling between them being disconnected. This is made possible in that the inside latching lever has an unlocking formation and a locking formation. Here the unlocking formation is effective on the central-locking pin for unlocking and the locking formation on the central-locking pin for locking. Both the unlocking formation and the locking formation move on pivoting of the inside latching lever through respective arcs about an axis of the inside latching lever.
The central-locking pin also describes on pivoting of the central-locking element about its axis an arc, namely the pin arc. The relative positions of the central-locking pin and the locking and unlocking formations are such that the arcuate travel paths of the formations and of the pin intersect when, and only when, in the locked and unlocked positions. However, when in the xe2x80x9cantitheftxe2x80x9d position the arcuate paths of the formations are spaced from the central-locking pin so that there can be no contact between the central-locking element and the inside latching lever in this position. As a result, when the inside latching lever pivots it has no effect on the central-locking element.
In addition the axis of the central-locking element and the axis of the inside latching lever are as a rule parallel to each other, both parts (that is the central-locking element and the inside latching lever) lying in separate planes and partially overlapping each other so that the desired interaction and thus intersection of the pin arc and the formation arcs are possible only for locking and unlocking.
According to the invention the antitheft element according to German 195 33 199 as well as the inside-locking button can be dispensed with. In other words the inside latching lever takes over both of these functions. This is made possible in that the inside latching lever is moved after each actuation by a spring into its rest position. In addition the inside latching lever is usually connected via an actuating rod or Bowden cable with an inside door handle so that locking or unlocking of the motor-vehicle latch requires a double actuation of the inside door handle. During a first actuation of the two-stroke inside actuation the latchxe2x80x94starting from the xe2x80x9clockedxe2x80x9d positionxe2x80x94is unlocked. During the second stroke of the inside handle the door latch is actually opened, in fact in the same direction. This is more fully described with reference to the description and drawing.
Overall with the illustrated motor-vehicle door latch the three positions, xe2x80x9cunlocked,xe2x80x9d xe2x80x9clocked,xe2x80x9d and xe2x80x9cantitheft,xe2x80x9d are established in an extremely simple mechanical way. Furthermore only one drive, namely the central-locking drive, is needed so that a prior-art separate antitheft drive is unnecessary. This is also true with the required antitheft lever of German 195 33 199. The mechanics only require very few parts as a result of two fork seats on the central-locking element defining four control surfaces. The described connection between the inside latching lever and the central-locking lever serves only for locking and unlocking so that as required in U.S. Pat. No. 5,240,296 blocking the central-locking element in the antitheft position is unnecessary. Finally the described motor-vehicle door latch can be opened in the xe2x80x9cantitheftxe2x80x9d position (from outside) by a locking cylinder with a locking nut. This ensures that in this position it is impossiblexe2x80x94even if the window is brokenxe2x80x94to open the actual door because the inside door handle is disconnected. These are the main advantages of the invention.